High-quality, c-oriented ZnO epitaxial films have been grown on the a surface using molecular-beam epitaxy. The use of a-oriented sapphire eliminates rotational domains and related structural defects which have limited the use of ZnO in electronic applications. The ZnO epitaxial layers are uniquely oriented with the ZnO/sapphire orientational relationship [0001]‖[112̄0] and 〈112̄0〉‖[0001]. This unique orientation is a consequence of the anisotropy of the a-sapphire surface in conjunction with a strong correlation along a single direction leading to the term uniaxial locked epitaxy. High-resolution x-ray diffraction measurements show an increase in x-ray lateral coherence length from several tens of nanometers to >0.7 μm for growth of c-oriented ZnO on the a surface as opposed to the c surface of sapphire.

The systematic variations in the structural, optical, and electrical properties of polycrystalline Cu͑In, Ga͒Se 2 ͑CIGS͒ thin films with Na doping level were investigated. Precise control of the Na concentration in CIGS films was demonstrated using alkali-silicate glass thin layers of various thicknesses deposited on substrates prior to CIGS growth. The CIGS grain size was observed to decrease with increasing Na concentration, although the surface morphology became smoother and exhibited a stronger ͑112͒ texture, which has been demonstrated consequence of larger grain size. The Ga composition gradient in the CIGS films was found to become large due to the presence of Na during growth, which in turn led to a decrease in the nominal band gap energy. Variations in the photoluminescence spectra and electrical properties suggested that the formation of an acceptor energy state, which may originate from O Se point defects, was enhanced in the presence of Na. This result suggests that not only Na, but also the presence of O in combination with Na contributes to the compensation of point defects and enhances p-type conductivity in CIGS films.

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Al-doped Zn1−xMgxO films have been deposited on glass substrates at a substrate temperature of 200°C by a pulsed laser deposition system. A resistivity of 3×10−4Ωcm was obtained at x=0.06. Film resistivity was found to increase with further increases in Mg composition. The maximum band gap of films with a resistivity ρ⩽1×10−3Ωcm was found to be 3.97eV, demonstrating band-gap engineering possibilities in the range of Eg=3.5–3.97eV with a resistivity ρ⩽1×10−3Ωcm. The average transmittance of the films was higher than 90% in the wavelength region λ=400–800nm, a range suitable for transparent conducting film applications.